This invention relates to the concentration of sulfide mineral ores by froth flotation using 1,3-oxathiolane-2-thiones as collectors.
Flotation is a process of treating a mixture of finely divided mineral solids, e.g., a pulverulent ore, suspended in a liquid whereby a portion of such solids are separated from other finely divided mineral solids, e.g., clays and other like materials present in the ore, by introducing a gas (or providing a gas in situ) in the liquid to produce a frothy mass containing certain of the solids on the top of the liquid, and leaving suspended (unfrothed) other solid components of the ore. Flotation is based on the principle that introducing a gas into a liquid containing solid particles of different materials suspended therein causes adherence of some gas to certain suspended solids and not to others and makes the particles having the gas thus adhered thereto lighter than the liquid. Accordingly, these particles rise to the top of the liquid to form a froth.
Various flotation agents have been admixed with the suspension to improve the frothing process. Such added agents are classed according to the function to be performed: collectors, for sulfide minerals including xanthates, thionocarbamates and the like; frothers which impart the property of forming a stable froth, e.g., natural oils such as pine oil and eucalyptus oil, modifiers such as activators to induce flotation in the presence of a collector, e.g., copper sulfate; depressants, e.g., sodium cyanide, which tend to prevent a collector from functioning as such on a mineral which it is desired to retain in the liquid, and thereby discourage a substance from being carried up and forming a part of the froth; pH regulators to produce optimum metallurgical results, e.g., lime, soda ash and the like. U.S. Pat. No. 3,464,551 discloses using dialkyl dithiocarbamates ##STR1## as flotation collectors; U.S. Pat. No. 3,590,996 describes flotation of sulfide ores using certain thionocarbamates.
It is of importance to bear in mind that additives of the above type are selected for use according to the nature of the ore, the mineral sought to be recovered, and the other additaments which are to be used in combination therewith.
An understanding of the phenomena which makes flotation a particularly valuable industrial operation is not essential to the practice of the present invention. They appear, however, to be largely associated with selective affinity of the surface of particulated solids, suspended in a liquid containing entrapped gas, for the liquid on the one hand, the gas on the other.
The flotation principle is applied in a number of mineral separation processes among which is the selective separation of such minerals as sulfide copper minerals, sulfide zinc minerals, sulfide molybdenum minerals and others from sulfide iron minerals.
Among commonly used collectors are the xanthates and the dithiophosphates. These collectors must be dried after preparation or shipped in solution which creates handling problems. Such collectors are relatively inexpensive but their activity as collectors is not as good as some other collectors.
Another class of commonly used collectors is the thionocarbamates. The preparation of these compounds normally requires a three-step synthesis, wherein salts and mercaptans are by-products. Such compounds are relatively expensive to prepare but have good activity. What is needed is a collector for sulfide ores which can be prepared in a simple synthesis scheme without the preparation of salt or mercaptan by-products. Further needed is a collector which does not necessitate drying or shipping in solution. What is further needed is a collector which is relatively inexpensive to prepare with good collector activity.